Pododermatitis – Rabbit

Also know as: Ulcerative pododermatitis — Sore hocks

Introduction

Pododermatitis is the epitome of a husbandry related disease. It is a complex, multifactorial condition involving musculoskeletal as well as integumentary systems.

The hind-leg stance of the rabbit is naturally digitigrade. Contact with the ground is through the claw and the plantar aspect of the hock. Most of the weight is taken on the hind limb. The superficial digital flexor is constantly under tension to facilitate immediate response to predators. The animal is therefore well adapted for life on grassland or turf.

All too frequently the pet rabbit is kept on unsuitable substrate and cannot bear weight normally on the claws. If weight-bearing is transferred to the plantar aspect of the metatarsus, pressure sores develop on the skin in that area. These can spread to subcutaneous tissues and, in advanced cases, the superficial digital flexor is displaced, which is a frequent finding in adult rabbits, particularly heavy adult bucks of which the feet become ulcerated due to contact with a dirty cage floor.

Risk Factors

Poor anatomical conformation:

large rabbits: giant breeds, obesity

lack of guard hairs: rex breeds, clipping of feet for surgery

Husbandry problems:

frequent thumping due to disturbances

inappropriate substrates: hard or abrasive surfaces, wire mesh

poor hygiene, damp, dirty bedding

Urinary/faecal incontinence

Loss of or lack of weight bearing of another limb

Stress factors affecting immune competence: chronic disease

Lack of mobility:

small cage

locomotor lesions such as spondylosis, ataxia

The most important factors are flooring construction and substrate, and wire mesh is the most likely to cause pododermatitis.

Clinical Signs

This condition is usually seen in the hind limb, but occasionally occurs on the palmar surface of the metacarpals.

The hock area may be erythematous with alopecia. There may be discharge from the skin. Ulcerations occur early on and progress to raised, thickened lesions covered in necrotic debris.

There may be cellulitis and the area involved may spread to include most of the tarsal and metatarsal area.

Secondary infections will exacerbate the ulcerations and may progress to involve the bone with osteomyelitis.

The pain may lead to ileus which will present as reduced fecal output and anorexia.

Diagnosis

Radiography should be performed to determine the extent of bone involvement. This will guide the treatment plan and help determine the prognosis.

Other radiographs may be performed to investigate the underlying cause of inactivity, such as spondylosis or dental disease.

If a mass is present, it can be biopsied or an aspirate taken to rule out neoplasia and granulomas.

A sterile, deep sample should be taken from the affected tissue, and culture and sensitivity should be performed to choose the best antibiotic therapy. Bacteria commonly isolated include Pasteurella multocida and Staphylococcus aureus - human strains of the latter often cause renal infarcts in rabbits. Corynebacterium pyogenes may also be involved.

Treatment

Treatment is challenging and not always successful.

It is essential to remove or correct the underlying cause for long-term success.

Nursing care involves: caging on soft, dry bedding may be sufficient in early disease. More severe disease requires frequent debridement and flushing of exudate and necrotic tissue and bandaging.

Bandaging: this is usually only necessary in open or debrided wounds. Wet-to-dry bandaging may be required until granulation tissue is formed. Silver sulfadiazine cream can be applied under the bandage.

Activity should be restricted until the wounds have healed, but encourage in the long-term.

Diet is an important consideration, as rabbits should never stop eating. Good quality grass hay and fresh greens should be offered. Critical Care formulas may have to be syringe-fed if the rabbit is reluctant to eat.

Surgical considerations: Debridement is extremely painful and should be conducted under general anaesthesia or deep sedation.

All necrotic tissue should be debrided. Abscesses should be drained, curetted, debrided and flushed copiously, as they commonly recur. The wounds should be flushed and debrided daily and bandaged.

Antibiotic-impregnated poly methylmethacrylate (AIPMM) beads can be placed in the wound to release a high concentration of antibiotics into the tissue.

Severe osteomyelitis may require amputation. Mid-femoral amputation is usually better tolerated. This may not be possible if bilateral disease is present.

Medical therapy involves:

long-term antibiotic therapy: ideally based on culture and sensitivity results, for 4-6 weeks minimum.

acute pain management: opiates such as buprenorphine or morphine, and NSAIDs such as carprofen or meloxicam, should be given

long-term pain management: NSAIDs such as carprofen or meloxicam

Client education is paramount: underlying diseases and husbandry problems need to be addressed for a successful outcome. Appropriate bedding needs to be used and wire flooring is not appropriate.

Clients must be aware of the monetary and time investments linked to this condition, due to the regular debridements, sedations and treatments necessary. Recurrences are also common, especially if the underlying cause cannot be corrected.

Amputation of the foot may lead to an increased risk of pododermatitis in the contralateral limb due to increased weight bearing.

Prognosis

The prognosis depends on the amount of tissue destruction.

Mild disease usually has a good prognosis, but these animals will always be at risk and should be closely monitored.

When osteomyelitis or tendon damage are present, the prognosis for return to normal anatomy is grave. The prognosis for return to functional weight bearing is variable and depends on the extent of bony involvement. Multiple surgeries, long-term antibiotics and follow-up is usually required as recurrences are common.

Animals with intractable pain may require amputation or euthanasia.

Prevention

Appropriate hutch substrates should be provided that are clean and soft.

A separate litter box can be provided to prevent the rabbit sitting in soiled litter for too long. Soiled substrates should be cleaned daily and bed wetting should be avoided (rain, spillages).

Obesity should be avoided by providing plenty of grass hay and fresh greens and avoiding muesli-type diets.

Exercise should be encouraged by providing large and safe spaces to encourage movement.

Pododermatitis – Rabbit Learning Resources
Flashcards Test your knowledge using flashcard type questions	Rabbit Medicine and Surgery Q&A 18

References

Harcourt Brown, F. (2002) Textbook of Rabbit Medicine Butterworth Heinemann Oxford ISBN 0 7506 4002

Okerman, L. (1994) Diseases of Domestic Rabbits Blackwell Scien¬tific Publications 2nd Edition

Oglesbee, B. (2006) The 5-minute veterinary consult: ferret and rabbit Wiley-Blackwell

Saunders, R. (2005) Notes on rabbit internal medicine Wiley-Blackwell